1. Field of the Invention
The present invention relates to an improvement in an optical information recording/reproducing apparatus which records/reproduces information on a recording medium and stops recording operation upon detecting an error in access operation to a target track.
2. Related Art and Prior Art Statement
Recently, with development of the information industry, attention has been focused on optical information recording/reproducing apparatus as memory devices of large capacity. Known one of these optical information recording/reproducing apparatus is an optical card device for recording and/or reproducing information by using an optical card as a recording medium. The optical card is not rewritable like an optical disk, but has a storage capacity on the order of 1 to 2 Mbytes several thousands to ten thousands time as much as that of a magnetic card. Therefore, the optical card is expected to have a wide range of applications such as banknotes, portable maps or prepaid cards for use in shopping and so on. Because of non-rewritable nature, other applications in which data should be tamper-evident, such as personal health care cards, are also expected. There have further been proposed a variety of optical information recording/reproducing apparatus adapted to record/reproduce by using optical disks in the form of a circular sheet as recording media.
Optical cards as recording media are grouped into, for example, the type that ID sections having track address information recorded therein are provided in both end portions of tracks parallel to one another (see Japanese Patent Laid-Open No. 63-37876), and the type that a data section of each track is divided into a plurality of sectors which are headed by a sector mark including no address information and comprising particular patterns (see Japanese Patent Laid-Open No. 63-193331).
In optical card devices for recording/reproducing data on and from such optical cards, the optical card is generally moved in a direction parallel to tracks to thereby read the ID section or the sector mark and record/reproduce data. When making an access to the target track in this type optical card device, a mechanism such as VCM for linearly moving the whole of an optical head including an object lens is used to move the object lens in the direction perpendicular to tracks in combination of a coarse seek (coarse access) in which the position of the entire optical head in the moving direction is detected and positioned by position detecting means such as a linear scale, and a track jump in which the object lens is moved on a track pitch by track pitch basis by tracking drive means. The coarse access giving rise to movement of the entire optical head is carried out in such a manner that an optical beam is positioned with some extent of an error (variation) relative to the target track after movement of the optical head, due to an offset of the object lens from a base position caused at starting and stopping of the movement, i.e., positioning errors such as caused by vibrations of optical cards as well as tolerances of the linear moving mechanism and the position detecting means. That error is usually within 10 tracks. In order to correct the error resulted from the coarse seek so that the optical beam is moved to the target track, the track jump capable of precise movement must be performed in the number of times corresponding to the difference from the target track.
The procedure of accessing to a target track on an optical card 30 shown in FIG. 3 will be described below with reference to a flowchart of the related art shown in FIG. 1.
The optical card 30 shown in FIG. 3 includes an information recording section 33 having a plurality of tacks 32 parallel to one another, ID sections 34a, 34b provided at both ends of the information recording section 33 to record therein address information corresponding to the respective tracks, and a data section 35 provided between the ID sections 34a, 34b for enabling the writing of information therein.
Let it be now assumed that the optical card 30 shown in FIG. 3 is stopped, an optical spot used for recording/reproducing is positioned at X1 in FIG. 3, and the track address of the position X1 is known. First, a step S21 in FIG. 1 calculates the track difference D between the address of the target track and the address of the current track (onto which the light spot is being illuminated). Then, a step S22 in FIG. 1 determines whether or not an absolute value .vertline.D.vertline. is smaller than a certain setting value a. If the decision is Yes (.vertline.D.vertline.&lt;a), then the control flow goes to a step S23 in FIG. 1 where the track jump is made by a distance corresponding to the track difference D, because moving the object lens by repeating the track jump needs a shorter access time than the coarse access of moving the entire optical head. Note that the setting value a is usually selected to be on the order of 4 to 10. On the other hand, if the decision in the step S22 is No (.vertline.D .vertline.&gt;a), then the coarse seek is performed to move the optical head by a distance corresponding to the track difference D in a step S23 of FIG. 1. The position of the light spot after the above movement by the coarse seek is indicated by reference character X2 shown in FIG. 3. Thereafter, while moving the optical card 30 in the direction of tracks in a step S25 of FIG. 1, the track address recorded in the ID section 34b is read out in a step S26 of FIG. 1 to confirm the track address after the movement by the coarse seek. Next, in a step S27 of FIG. 1, whether the target track is reached or not is determined from the track address read out of the ID section 34b. Here, when the optical head has been moved by the track jump in the step S23 of FIG. 1, the target track is reached in most cases because of high accuracy of the track jump operation, but when it has been moved by the coarse seek, the target track is rarely reached for the reasons mentioned above. If the decision in the step S27 is No, then a step S27 in FIG. 1 waits a predetermined period of time for that the optical card 30 is moved to the opposite end for positioning the light spot at X3 in FIG. 3 and stopped, followed by returning to the step S21 in FIG. 1 after the predetermined period of time. The difference between the position X3 and the target track usually holds the relationship of .vertline.D.vertline.&lt;a and, therefore, the light spot is now positioned to X4 in FIG. 3 by making the track jump by a distance corresponding to the track difference D. If the decision in the step S27 is Yes, then read/write operation of data is performed in a step S29 of FIG. 1 because the address is in match with the target track.
Meanwhile, as related art Japanese Patent Laid-Open No. 03-100972 and No. 03-147573 disclose means for improving reliability of recorded data when data is recorded on an optical card. In Japanese Patent Laid-Open No. 03-100972, the detection criterion for a synch signal contained in track address information preformatted on an optical card is made severer during the recording of data than during the reproduction of data and the seek to a target track, thereby preventing data from being recorded on those tracks of which address information is hard to read. Accordingly, even with deterioration occurred over time, data can be recorded on tracks under good condition. In Japanese Patent Laid-Open No. 03-147573, the error detecting and correcting capability for track address information preformatted on an optical card is made lower during the recording of data than during the reproduction of data and the seek to a target track, thereby preventing data from being recorded on those tracks of which address information is hard to read. Stated otherwise, a possible risk that the address cannot be properly read at the present or in future is checked beforehand to disable the writing of data on those tracks having such a risk.
However, when an optical head is moved toward a target track on an optical card and once landed on some track near the target track, an error such as a track/focus offset may occur due to a defect, dust or the like on the track other than the target track. Further, when repeating the track jump from some track near the target track to the target track, a track servo system is once turned off and pluses are applied to an object lens actuator to move an object lens by one track. Then, after vibrations of the object lens are settled to a satisfactory extent, the track servo system is turned on again. In this connection, if a defect, dust or the like on the optical card is present at a position where the track servo system is turned on, the positioning of a light spot over tracks may be failed such that the light spot lands on other track apart from the one intended by the track jump, or in the worst case, a focus servo system may come out of the coverage. Such an event appears more significantly when the track jump is made through the so-called double servo mode. Further, when repeating the track jump plural times, a risk of abnormal track jump is enlarged as the number of repeated times increases.
In the event of such a drawback, prior art apparatus have taken the following measures to cope with it. The optical head is once returned to the home position set by the linear scale, for example, to recognize the track address at which the light spot is positioned at the present, followed by trying movement .operation to the target track a predetermined number of times. If the retry operation has succeeded in making the light spot reach the target track within the predetermined number of times, recording/reproducing operation is carried out without judging such a condition as a significant error. This type technique is described, by way of example, in Japanese Patent Laid-Open No. 2-235200.
The above retry operation is very effective in reading data on the optical card, but produces a contrary effect when recording data on the optical card. Specifically, if the size of a defect, dust or the like is on the borderline whether to cause a track offset or not, it may happen that a seek was succeeded accidentally at the time of recording data, but an access fails to succeed during the subsequent reading of data. This results in a serious trouble that the recorded data cannot be accessed.
Additionally, in the above-cited Japanese Patent Laid-Open No. 03-100972 and No. 03-147573, when the preformatted track address or synch pattern is hard to read during the recording, data is prevented from being recorded on the relevant track. However, no explanations are found about a track offset and the above-stated disadvantage is thought to inevitably occur in those references.